We all have been in situations where things look really bad and you are not sure how you are going to recover. That is the time when experience really helps. You know you have been in tough situations before and survived and even succeeded. Although that sounds a bit trite, I have found it really helps and gives me courage and encouragement.
Another approach I have taken is a strategic management approach. The goal is not to boil the ocean but improve the situation. Consider the next steps that can improve the situation. Wishing it were not so or denying reality does not help. Taking action is the best therapy and most useful. Procrastinating or wishing it were not so takes much more energy than action.
In golf, fussing about the last lousy shot, does absolutely no good. Only thing you can do is take the next shot that improves your chances of getting a decent score. In sailing, fussing about the lousy start does not help improve your position in the race. What helps is making a better decision, right now.
"The moving finger writes and have writ moves on. All your piety or wit, cannot lure it back to cancel half a line." Omar Kyram.